1. Field of the Invention
The present invention relates in general to particle beam generation sources, and relates in particular to a particle beam generation source which is capable of generating a plurality of beams of different energy levels by impressing different types of electrical voltage on electrodes of a beam discharge tube to perform different fabrications. The present invention relates also to a micro-fabrication apparatus for conducting simultaneous or serial fabrication processes on one workpiece by using the energy beam source of a compact design. The present invention also relates to a method of making suitable patterns on any surface of fine parts such as micro-machines and semiconductor elements. The energy beam source of the present invention is employable to micro-fabricate a pattern of the order of nanometer spacing (nm), for example, disconnecting/connecting wiring patterns or fabricating a three-dimensional architecture on an insulating substrate base.
2. Description of the Related Art
Conventional particle beam sources such as ion beam sources and other beam sources for forming charged ions or radical particles in plasma processing are provided with a fixed applied voltage because such beam sources are generally designed to be used for one end objective, and require only one type of particle beam to be generated therefrom. For example, in ion beam sources, the ion acceleration electrode is supplied with a direct current voltage, and the ion energy beam is varied by varying the magnitude of the applied direct current voltage. The ion beam source of such a design is generally not capable of generating other types of particles.
Energy beams are used in photolithographic processes to carry out micro-fabrication of fine semiconductor patterns. A basic photolithographic process of fabricating semiconductors is explained in the following.
FIG. 20 shows a conventional micro-fabrication process using photolithography. In Step 1, a semiconductor substrate base 1 is coated with a photoresist material 2. In Step 2, ultraviolet (UV) light 4 is irradiated through a photomask 3 to transfer pattern holes 3a of the photomask 3 to the photoresist coating 2. In Step 3, through a development process, those areas of the photoresist material 2 which were exposed to the UV light 4 through the patterns holes 3a are removed. By utilizing ions and radical particles in a plasma discharge, anisotropic etching is performed in Step 4 on those areas which are not protected by the photoresist coating 2. The final step, Step 5, is the removal of the photoresist coating. At least the above series of basic steps are required to produce cavities 1c of the same pattern as the pattern holes 3a of the photomask 3 on the surface of the substrate base 1. The usual practice for fabricating a semiconductor device is to repeat the above series of basic steps combined with introduction of dopants at selected stages of the photolithographic process.
Also, conventional methods of forming a film deposit on a surface of electronic parts, fine machinery parts and medical devices involve some vacuum deposition or sputtering process.
As shown in FIG. 31, a vacuum deposition process comprises the steps of: heating a target material 6 in a vacuum vessel 5 with a heater 6a; vaporizing the target material 6 to deposit a vapor on a workpiece 7, such as a substrate base, to be coated; depositing a film 6c by continuing the vaporizing and coating processes. The method of heating includes resistance heating, radiation heating and electron beam heating.
A sputtered coating is formed by enclosing a substrate base 7 in a vacuum vessel, as shown in FIG. 32, and a high energy beam such as an ion beam is radiated from a beam source 8 to a target source 9, and sputtered particles 9a, which is a secondary emission product from the target source 9, are deposited on the substrate base 7 to form a sputtered coating 9b.
There are several inherent problems in the conventional technology that limit the production capability of deposit making devices. These problem will be discussed in some detail in the following.
According to the conventional photolithographic method presented above, it is difficult to produce patterns of ultra-fine line widths or diameters, and at the present time, special approaches are needed to produce finer patterns than those generally available.
Also, the ion beam source is usually fixed on a flange and the degree of freedom of orientating the source is severely limited. Consequently, it is difficult to position the beam source so that any surface of a workpiece may be irradiated, and it is especially difficult to employ a plurality of energy beam sources to perform a three-dimensional irradiation on the workpiece.
Also, in micro-fabrication processes on semiconductor materials using the conventional photolithography technique, it is necessary for the substrate base to have certain surface qualities, such as high flatness, and those bases having poor surface finish, or bowing are rejected. Furthermore, it is, difficult to produce a photoresist pattern on more than one surface of one workpiece at any one time. This is because transfer of each pattern requires preparation of a photomask, thus necessitating the preparation of a photomask for each pattern. It will be understood that the entire process is quite cumbersome and expensive, and limits the degree of freedom of pattern making on the substrate base. Therefore, there is a need for developing a new technology for pattern transfer and etching processes.
Another problem of conventional methods is that if an ion beam source or electron beam source is used to remove a photoresist coating, in addition to having such beam sources, it is necessary to have a reactive gas supply facility. Further, the ion beam source or electron beam source is fixed to a flange, and as mentioned earlier, although a certain degree of movement of the workpiece is feasible, such movement basically is restricted to a two-dimensional fabrication task on one surface of the workpiece. It is even more difficult to perform fabrication on one selected spot of the workpiece using freely selectable beam sources and different incident beam angles.
As summarized above, the conventional film deposit forming processes are designed to produce a pattern uniformly overall on a selected surface of a workpiece, and they are not suitable for producing desired patterns on selected surfaces or locations on the workpiece. The result is that it is difficult presently to produce a high performance assembled part from several microsized parts or to produce a film deposit on complexly shaped articles.
In other words, assembling of micro-parts or forming a film deposit on a complexly shaped part requires that a deposit of a certain pattern is formed on a selected surface or on a restricted location of a workpiece. However, the conventional methods are designed for forming a film deposit of uniform characteristics and are inadequate to meet the growing demand for a more flexible and adaptable system for performing micro-fabrication in a three-dimensional space.